The server I manage also used the inaccessible groups being grayed out but visible as a way to organize groups in combination with i_group_sort_id for the "Set Server Group right click context menu. Now admins have a harder time quickly finding the needed tag since the list is all blended together.
Example of our group headers (note screenshot is from server groups window):
It’s similar in setup to the below thread on the old forum:
It would be great to have this feature back, or possibly add a group type for headers or a permission to make a group exempt from being hidden.
edit note: clarified the suggestion/feedback is for the right click “Set Server Group” menu on a user.